Poliovirus, adenoviruses and murine oncornaviruses will be examined in a continuing effort to identify and characterize the macromolecular processes occurring during their replication in human cells. The structure of functioning poliovirus replicase, adenovirus infected cells and subcellular fractions, and RNA genomes and messages will be studied by electron microscopy and protein physical chemistry. Attempts will be made to develop electron microscopic methods for obtaining sequence-related information from proteins along the lines of those used for nucleic acids.